Mechanical and chemical-mechanical planarization and polishing processes (collectively “CMP”) remove material from the surfaces of microfeature workpieces in the production of microelectronic devices and other products. FIG. 1 schematically illustrates a rotary CMP machine 10 having a platen 22, a polishing pad 20 on the platen 22, and a carrier 30 adjacent to the polishing pad 20. The CMP machine 10 may also have an under-pad 23 between an upper surface 26 of the platen 22 and a lower surface of the polishing pad 20. A platen drive assembly 24 rotates the platen 22 (as indicated by arrow F) and/or reciprocates the platen 22 back and forth (as indicated by arrow G). Because the polishing pad 20 is attached to the under-pad 23, the polishing pad 20 moves with the platen 22 during planarization.
The carrier 30 has a carrier head 31 with a lower surface 33 to which a microfeature workpiece 12 may be attached, or the workpiece 12 may be attached to a resilient pad 32 under the lower surface 33. The carrier head 31 may be a weighted, free-floating wafer carrier, or a carrier actuator assembly 34 may be attached to the carrier head 31 to impart rotational motion to the microfeature workpiece 12 (as indicated by arrow J) and/or reciprocate the workpiece 12 back and forth (as indicated by arrow I).
The polishing pad 20 and a polishing solution 21 define a polishing medium 25 that mechanically and/or chemically-mechanically removes material from the surface of the microfeature workpiece 12. The polishing solution 21 may be a conventional CMP slurry with abrasive particles and chemicals that etch and/or oxidize the surface of the microfeature workpiece 12, or the polishing solution 21 may be a “clean” nonabrasive planarizing solution without abrasive particles. In most CMP applications, abrasive slurries with abrasive particles are used on nonabrasive polishing pads, and clean nonabrasive solutions without abrasive particles are used on fixed-abrasive polishing pads.
To planarize the microfeature workpiece 12 with the CMP machine 10, the carrier head 31 presses the workpiece 12 face-down against the polishing pad 20. More specifically, the carrier head 31 generally presses the microfeature workpiece 12 against the polishing solution 21 on a polishing surface 27 of the polishing pad 20, and the platen 22 and/or the carrier head 31 move to rub the workpiece 12 against the polishing surface 27. As the microfeature workpiece 12 rubs against the polishing surface 27, the polishing medium 25 removes material from the face of the workpiece 12.
The CMP process must consistently and accurately produce a uniformly planar surface on the microfeature workpiece 12 to enable precise fabrication of circuits and photo-patterns. One problem with existing CMP methods is that the polishing surface 27 of the polishing pad 20 can wear unevenly or become glazed with accumulations of polishing solution 21 and/or material removed from the microfeature workpiece 12 and/or the polishing pad 20. To restore the planarizing/polishing characteristics of the polishing pad 20, the pad 20 is typically conditioned by removing the accumulations of waste matter with a conditioner 40. Such conditioners are available from Applied Materials of Santa Clara, Calif. under the trade name Mirra.
The existing conditioner 40 typically includes an abrasive end effector 41 having a head 45 generally embedded with diamond particles. The head 45 is attached to a single shaft 42 which connects to a shaft housing 72. The shaft housing 72 is supported relative to the polishing pad 20 by an arm 43 and a support housing 44. A motor 51 within the support housing 44 rotates the shaft housing 72, the shaft 42 and the head 45 (as indicated by arrow A) via a pair of pulleys 53a, 53b and a connecting belt 54. The conditioner 40 can also include a separate actuator (not shown in FIG. 1) that sweeps the arm 43 and the end effector 41 back and forth (as indicated by arrow B). A bladder 71 rotates with the shafts 42 and applies a normal force to the head 45 (as indicated by arrow C) to press the head 45 against the polishing pad 20. In another arrangement (available from Ebara Corporation of Tokyo, Japan), a non-rotating air cylinder counteracts the dead weight of the head 45 to regulate the down-force applied against the polishing pad 20. In either arrangement, the typical end effector 41 removes a thin layer of the polishing pad material in addition to the waste matter to form a new, clean polishing surface 27 on the polishing pad 20.
One drawback associated with the arrangements described above with reference to FIG. 1 is that the drive belt 54 typically wears out at a relatively rapid rate. Accordingly, the operator of the CMP machine 10 must spend a significant amount of time replacing the belt 54, which reduces the throughput of the machine 10. Furthermore, as the belt 54 wears and fails, it can contaminate the polishing pad 20 with debris, which can interfere not only with the conditioning operation but also with the polishing operations conducted on the polishing pad 20. Still further, when the machine 10 is operated in an autonomous manner, the belt 54 can fail without an automatic provision for halting the sweeping action of the arm 43. As a result, the head 45 can sweep back and forth without rotating, which can condition the polishing pad in an uneven manner and/or create an uneven wear pattern on the abrasive surface of the head 45.
Another drawback associated with the system described above with reference to FIG. 1 is that the bladder 71 (used to apply a normal force to the head 45) can fail after a relatively short duty cycle, further increasing the amount of time and money required to keep the machine 10 operational. Still further, the operator must often over-pressure the bladder 71 to overcome a threshold inflation resistance, and then reduce the pressure to apply the desired force. This can result in inconsistent down-forces applied to the polishing pad 20, which can in turn lead to inconsistent polishing pad conditions, and ultimately, inconsistent surface conditions on the workpiece 12.